The delay between sending a request and receiving a response. Like the time it takes between asking a question and getting an answer.
Online gaming requires low latency - players notice if there's more than 50 milliseconds delay between their actions and the game response.
Latency is a general networking concept and does not have direct service equivalents in cloud provider offerings. However, cloud providers offer various services to optimize and reduce latency, such as content delivery networks and edge computing solutions.