Latin is an interesting language. Not only has it had a profound effect on our world today (being the common ancestor of all Romance Languages) but its grammar, history of use, and cultural identity is something you don't see talked about much today.
Latin is a language that has had a profound effect on the western world. While really only being used commonly until the late first millenia until evolving into the various Romance languages, Latin continued to be used as a religious, scientific, and literary language throughout the 1000s. Because of this, basically everything that was intellectually significant from the Romans up until the late 1000s is in Latin, and that knowledge is still important today! Plus, because Latin later evolved into today's Romance languages, which are spoken by billions of people, you get a very strong foundation for learning those.
Latin's grammer is highly inflected. That means that each word in Latin belongs to a certain grammatical category. For example, take the english sentence "The boy kicked the ball to his friend". We can easily break down this sentence into different parts. We have the subject, boy which is the person doing the action. The verb, kicked, which is the action itself. The direct object, ball, which is the thing being kicked. Finally, we have the indirect object, his friend, which is whom the boy is kicking the ball to.
Basically, Subject = The one doing the verb, Verb = The action being done, Direct Object = The object of the action, and Indirect Object = The recipient of the action. Get it? Good. As you may of noticed, in English, everything centers around the verb. Every word in the sentence gets its form from the verb. The word order of English is also subject, verb, object or SVO, but that doesn't matter much right now.Latin is different.
In Latin, every word's form is related to it's function in a sentence. Let's break down the simple phrase "Aemilia femina Romana est." Just by looking at it, you might be able to decipher it: Aemilia is a Roman Woman. but, we could also say it like "Aemilia est femina Romana" or even "Femina Romana Aemilia est." Word order is so flexible in Latin because each word belongs to it's own grammatical category. Aemilia is the subject (or nominative noun) of the sentence, and if she were the direct object (accusative noun), she would be Aemiliam.
Because each word of a sentence, even names, are declined (the form, or case a noun takes), or conjugated (for verbs), there is no ambiguity when you see a single word. We know immediately that Aemiliam is the direct object, because of its case. This allows the words of a Latin sentence to be in any order (though authors usually go for Subject, Object, Verb or Subject, Verb, Object). With English, if I say the word "ball", I have no idea if the ball you're reffering to is a subject, direct object, or indirect object. This is why English has a word order.So what are the Latin cases?
Each Latin noun can fit into 7 different cases: nominative, vocative, accusative, genitive, dative, ablative, and locative. The locative case really only deals with a small amount of nouns such as cities and islands, so you can basically just throw that one out the window for now. But what about the others? Well, it's quite easy!
There's also grammatical gender, but thats more or less the same in what you see in modern Romance languages.
Ok! Thats enough grammar for now. If you want to actually learn Latin, here are some good resources!
In general, it's usually better to learn a language with older books. The same applies to Latin, and luckily these older books are considered the "go-to" for learning the language.
This is the cream of the crop when it comes to learning Latin. Lingua Latina per se Illustrata is a Latin instructional book entirely in Latin. Even the copyright page! Almost magically, you can understand the first page. It employs what is known as the Natural Method, which is a way of teaching languages by exposure, and LLPSI does a very good job at it. It includes pictures to help you learn new words and notes in the margins to help you learn grammar. Additionally, there are tables and exercises at the end of each chapter, and I cannot stress enough that you need to do your exercises. Skipping over these means you won't learn Latin, simple as that.
Lingua Latina is avalible to buy on Amazon and on the original publishers site, both for around the same price. I heavily recommend buying the physical book (and from Hackett, so you don't support Bezos), as I've found it way easier to learn the language hands-on, but it's probably perfectly doable to read it digitally. In fact, if you think that's what works for you, I encourage you to pirate it. Here are some links you can use.
Also, don't translate! Read and do the exercises, try and actually think in Latin!
I consider this a good companion piece to LLPSI. Its intro explains English grammar pretty well (albeit in a dated way) and it does the same for Latin grammar. The exercises here are also pretty worthwhile to do, although some are considerably harder than LLPSI's. You can also buy it on Amazon, but it's a reprint of UC Berkeley's library copy so it has a few marks. Collar and Daniell's is in the public domain, so you can find the PDF of it on archive.org here
If you hear a website suggesting you use the Dowling Method, don't use it. The Dowling Method is built upon writing down your noun declension and verb conjugation tables 100s of times to brute-memorize them. If this is your thing, go ahead, but I'm going to take a guess that it isn't. It is incredibly boring and painful, and only serves as demotivating the potential Latin student. I recommend writing the tables down a few times, but in my personal experience LLPSI and Collar and Daniell's is more than enough.
An essential part of learning a language is exposure to it. Thus, here are several communities centered around Latin and speak it.