Ichidan means they have one way of being said, godan means they have five.
Also known as ru and u-verbs for the following reason.
Ichidan/ru:
たべる (eat)
おきる (get up)
かりる (borrow)
あびる (bathe)
These verbs end in る, and, when conjugated, only add something after the stem, that is, the part before る.
For example:
たべない (negative)
たべます (masu)
たべる (dictionary)
たべられる (potential/can)
たべよう (volitional/let’s)
おきない
おきます
おきる
おきられる
おきよう
かりない
かります
かりる
かりられる
かりよう
あびない
あびます
あびる
あびられる
あびよう
In all of these, the two first syllables (i.e., the stem) don’t change, and as such, they’re always said one way.
Godan/u:
のむ (drink)
ねむる (sleep)
かす (lend)
はしる (run)
These verbs end in う つ る む ぶ ぬ す く ぐ, and, when conjugated, the last syllable changes accordingly.
The reason I arranged the ichidan verbs as negative, masu, dictionary, potential/can, and volitional/let’s, is because the godan verbs use a different vowel for each of these forms.
For example:
のまない ー あ
のみます ー い
のむ ー う
のめる ー え
のもう ー お
ねむらない
ねむります
ねむる
ねむれる
ねむろう
かさない
かします
かす
かせる
かそう
はしらない
はしります
はしる
はしれる
はしろう
In all of these, the last syllable changes, and as such, they can be said in five different ways.
Because of this, ichidan verbs are easy to conjugate, and godan verbs take a bit more work, but still follow simple rules.
Does this help?
A dictionary like jisho.org or takoboto can tell you what kind of verb it is, and its conjugations.