[Cola]

So in the dictionary the verb end in "ru る"?
But what is this "to と" in the verb?
Kaitoru かいとる

Dictionary form verbs may end in う, つ, る, む, ぶ, ぬ, く, or ぐ. As far as conjugation goes, there are two types of verbs in Japanese, plus three irregular verbs (and all the compound verbs tacked on to those irregular verbs). In Japanese classes, these two categories are often referred to as う-verbs and る-verbs or as type 1 and type 2 verbs. This has nothing to do with transitivity, only conjugation. The dictionary form of う-verbs may end in any of the endings you see above, including る. る-verbs only end in る and conjugate differently from う-verbs. As you can see, there is some overlap, as both う- and る-verbs may end in る. However, a verb that ends in る can only be one type or the other - if you see a dictionary form of a verb that ends in る and don't already know which type it is, you won't be able to tell which one it's supposed to be; in this case you just have to already know which type it is. If you don't know, you'll have to look it up or ask. If it's conjugated, however, you'll know immediately, because the forms are distinct.

To conjugate う-verbs into ます/ません form, take the ending hiragana character (the above-mentioned う, つ, る, む, ぶ, ぬ, く, or ぐ), change it to the い-form in the same hiragana group, and add ます or ません. So, for example, う becomes い, つ becomes ち, る becomes り, etc. (it can be easier to think of it using English spelling to start - take the last "u" and turn it into an "i", so "u" becomes "i", "tsu" becomes "tsi" but there is no "tsi" in Japanese so it must be "chi", "ru" becomes "ri" - gotta use your head a bit). So, かう (to buy) becomes かいます, かつ (to win) becomes かちます, はしる (to run) becomes はしります etc.

With る-verbs, just cut off the る and add ます/ません. You already know one る-verb - たべる. Cut off the る, add ます and you get たべます.

You already know the only 3 irregular verbs in Japanese - する (to do), くる (to come), and いく (to go). You just remember their conjugations, which are する - します/しません, くる - きます/きません, and いく - いきます/いきません. As I briefly mentioned above, however, there are many compound verbs that use these three irregulars as their ending. You just conjugate them the same way you conjugate the plain irregular verbs.

There are more conjugation forms than this, but you'll learn them as you go along.

かう is the basic word for "to buy". かいとる would be a word to use when a business buys something or purchasing made in a business context, like buying out another company. You should probably only need かう right now.