The word "лишь" is very rarely used in colloquial speech (maybe because the sound "ш" is difficult for some people, even Russians). However, that word is very often used in songs and poetry.
The word "только" is a normal colloquial word. It usually means the same as "лишь".
The word "только" has a lot of other meanings like "just", "merely", "but" etc.
The combination "лишь только" may be used for emphasis. It also can mean "as soon as".