I’m no accountant (as the CPA reminded me .. hahaha) but basically IRAs are retirement plans you open as an individual with a brokerage or other entity while 401ks (and 403b) are managed through your employer, and may be eligible for matching funds from the employer and other benefits.
There are other differences such as max allowed $$ contributions per year for each plan, whether loans are allowed, etc. At this point an expert should chime in.
Is it possible to roll the current 401k into an IRA so I'll have more control over it? Also, my employer recently offered Roth IRA plans, but I don't really understand that option either.
As an aside, I really don't like the Vanguard IRA... they really limit you on what funds you can buy into, and they offer no PMs or gold ETFs unless you've got beaucoup $$ to put in to start off.