たべる　（Dictionary form and ｓhort form - Now or future） たべた　（Short form - past） たべます　（Long form - now or future） たべました　（Long form - past） たべて　（てーform） This is all the same word conjugated in different ways and there is still a ton more ways to say it. Dictionary form is the one you'll find in a dictionary. To learn these forms properly, I'd recommend getting the Genki textbooks, I find them very good, I haven't tried any others, but look for books on conjugations, I suppose?

I hope this will help you! I wrote it with space so it's easier for you to read it. にほんご を べんきょう します= I study Japanese. (present + future ) あした, にほんご を べんきょう します = I'll study Japanese tomorrow にほんご を べんきょう して います = I'm studying Japanese にほんご を べんきょう しました = I studied Japanese にほんご を べんきょう したい = I want to study Japanese にほんご を べんきょう して ください = Please study Japanese にほんご を べんきょう しません = I don't study Japanese にほんご を べんきょう したくありません = I don't want to study Japanese きょう = Today あした = tomorrow あさって = day after tomorrow きのう = yesterday おととい = day before yesterday いま = Now いつ = When よじ = 4 o'clock きょうカラオケにいきます = I'll go to the Karaoke today. ( カラオケ = karaoke )