Japanese verbs have all sorts of conjugations, but the first conjugation we'll learn is the ます (masu) form. What is the ます form? Japanese has different levels of honorific speech. Also known as the long form, the ます form is the polite way of speaking when describing actions of yourself and others. Along with ます, polite language also includes the usage of です (desu).
So, let's recall that there are two different kinds of verbs (well kinda, there's three):
る- verbs: verbs ending in る (i.e. たべる taberu = to eat)
う-verbs: verbs ending in う (i.e. のむ nomu = to drink)
Irregular verbs: verbs having irregular conjugation (する suru = to do, くる kuru = to come)
When we conjugate these verbs to the ますform, we use a certain method for each verb (for the irregular verbs, they have their own unique conjugation).
For る- verbs: drop る, and add ます.
For example, たべる becomes たべます.
For う-verbs: drop the -u ending, and add います. *
For example, のむ becomes のみます.
As for irregular verbs, する becomes します, and くる becomes きます. **
*The -u ending to the う-verb is replaced with -i, and then -masu is added to it. In the example used, のむ (nomu), you remove the -u, giving you noM. You replace it with -i, making it noMI. You then add -masu, making it noMImasu. The character changes from む (MU) to み (MI) because you replaced -u with -i, thus changing the sound. Other examples of う-verb endings look like this:
く becomes き, such as きく (kiKU = to listen) conjugating to ききます (kiKImasu).
る becomes り, such as かえる (kaeRU = to return) conjugating to かえります (kaeRImasu).
**These are really the only two irregular verbs, so just remember them as they are.
Keep in mind though that what we've just learned is the PRESENT AFFIRMATIVE tense for the ます form. In the next lessons, we'll learn about the present negative, past affirmative, and past negative.