Meaning: This sentence is an invitation to join a meal. It means that the food is ready and it's time to gather around the table to eat.
Choice of Words: "It's" is a contraction of "it is." "Time" refers to a specific moment or period when something should happen. "Eat" means to consume food. "Dinner" is the main meal of the day, typically eaten in the evening. "Come" means to move towards a place. "Table" is a piece of furniture with a flat top, typically used for eating or working.