> Any basic advice for someone on these things?

Follow the Prime Directive: https://www.reddit.com/r/personalfinance/wiki/commontopics

> Or is there a wiki

Yes, this sub has a detailed Wiki.

https://www.reddit.com/r/personalfinance/wiki/

> I am foreigner working in the US on a visa (not an h1b) and i have no idea about the 401k or the roth.

A lot will depend on whether you intend to retire in the US or if you plan to retire elsewhere. Many countries don't recognize US Roth accounts. See: https://creativeplanning.com/international/insights/expat-roth-conversions-qa/

The primary difference is taxation. Anything that is designated as a "Roth" is funded with money that has already been subjected to taxation by the government. All other retirement accounts are funded with money that has not been taxed by the government, YET.

The government will get their taxes from those pre-tax accounts when you withdrawal the funds in retirement.