16 pixels by 16 pixels is a common resolution for assets matching a low-res pixel art aesthetic. Although the assets may not be specifically 16x16, they are designed to work in a graphical setting where objects are around that size.
A turn-based game mechanic is the opposite of a real-time game mechanic. In a Turn-By-Turn mechanic (synonym), each player has to wait for the other to have played, so that they can play, and so on. This way, each player has the time to think about their strategy. TBT games rely less on action than real-time games.
