This is sort of a beginner's question but I seem to have trouble understanding this. I can never remember la or el or all the other ones on which word they go on. There doesn't seem to be a rule for how to know, and I just can't figure it out, or remember. Any tips on knowing which is which, and why?? or how??
Probably the largest, and most difficult part of learning a language is plain old memorization. You need to memorize hundreds, thousands of words to be fluent.
When you learn english, you basically memorize how to pronounce every word, since there are no rules for pronunciation. In spanish, there are rules for pronunciation and accents, so you can read any word correctly if you know the simple rules, even if you don't know the meaning. On the other hand, you basically need to memorize the gender of every noun out there that has a gender. Since there are nouns that never have a gender: there is la guitarra, but there is no el guitarro.
There are also words such as la lavadora in México, are el lavarropas in Argentina. So you might be tempted to think appliances in Mexico are female, and they are male in Argentina. But you'd be wrong, since there is also la licuadora or el televisor in both countries. So yes, you also need to know which variation of spanish you are speaking, in order to know which word gender to use.
Oh, and gender can make a word change meanings significantly. La puta means something completely different from el puto.
As for why words have gender, I suppose the best answer is because. Also you seem to be confused by articles: el, la, los, las. English makes it easier with simply the, but Russian makes it even easier... with no articles at all. German, on the other hand...
Also, if you're an English speaker, you will be surprised that there is a past, present, and future tense, which in English it uses an auxiliary word, but in spanish it's a completely different conjugation: was, am, will be are fui, soy, seré.