You either saw a valve with compression fittings or most likely based on your description you saw a "Shark Bite" fitting. Both of these are solderless and can be trusted.
If you prefer to solder, I'd use a metal heat sheild with a wet towel behind that.
However, I use an asbestos rag made for soldering against flamable surfaces.
Note: the Shark Bite fitting requires a special tool to remove and is sold separately from the fitting itself. The compression fitting will require cutting back an about an inch of pipe from both sides upon removal.
Personally, I'd go with the shark bite fitting and they are somewhat expensive but cheaper than you insurance deductible if you burn down the house. As far as the tool, it's kinda like undoing a gas line fitting on an automobile, you just need something thin to wrap around the pipe and slide into the fitting while pulling the connection apart. I made one out of a beer can but, you have to be careful not to cut yourself on the aluminum (wear gloves and do it after the first beer not the sixth).