Stranded knitting involves holding two colours at once, often one in each hand, when a colour isn't used it's passed behind the knitting, usually for no more than 5 stitches. FI is a type of stranded knitting but people generally use FI to mean the same thing. Most colourwork mittens have stranded knitting-type motifs/patterns.
Intarsia is the kind that you have probably seen on jumpers with a cartoon character on the front in different colours. See the videos here on how-to or find tutorials online. Knitty has a good explanatory article on stranded knitting.
If you want a single biggish bike on the front of a jumper etc. you probably need intarsia. The simpler the motif, the easier it will be to knit.
The snowflake or geographic-type motifs you often see on hats or mittens are stranded knitting, if you see a cartoon character on the middle front of a jumper that's probably intarsia - does that make sense?
Maybe try searching both methods in the FO forum to see examples?