the /24 means that the corresponding IP address is a part of a /24 subnet. in short it means that the first 24 bits of the IP address is being used as the network ID, and the rest bits are used as host ID. the subnet mask would look like this:
see the sticky in the Basic Concepts on how to subnet classes A, B and C IP addresses for a comprehensive explanation
Picking pebbles on the shore of the networking ocean
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