First picture is a valley which is typically flashed with metal and acceptable way of installing. Picture two is your ridge cap installed over the ridge vent, typically stopping short of the roof end, and again perfectly normal. Pictures three and four show a side wall flashing, again in a colored metal and perfectly normal. On the third picture tough to tell what is happening with the lower left corner shingle but that may need to be addressed. All in all, looks like what a new roof would look like, save that one potential issue.

If it doesn't leak, there doesn't appear to be anything unusual.

Everthing as millworkman said, these are all parts of a roof.

I think the 3rd picture is the step flashing that got some drips of paint or the metal paint wore off.

As others have said what you are seeing are ridge vents and flashing. Unless your attic space has spray on insulation the attic space needs to be vented. That is what the ridge vent does. It allows air flow from soffit vents the ridge vent. I have seen valley flashing done like yours but, in general, the roof shingles cover the metal valley flashing. In general though your roof looks like millions of others. I would only concern myself if it starts leaking.

Open valleys like on the OP's roof are typically preferred where snow and ice are expected or where debris may accumulate in a valley.