401k in the US

Hello

I am a bit noob in this business and I would like to hear your opinion
My company has started to offer 401k (pension plan in the u.s)
As part of the plan you can invest the money in different financial tools such as bonds or the stock market
Using companies and investment houses such as "DAVIS" (in ny) "American funds" "fidelity"
And such

I have control(partial) on where my money would be invested
And can select if to go on an aggressive plan (stocks only) conservative plan(bonds) or combination of the two

I would like to hear your opinion on a long term investment and on those financial tools


Thanks a lot


Matan