echo means several things in computing.

Terminal command

echo is a command in Unix (and by extension, its descendants, such as Linux) and MS-DOS that places a string on the terminal. It is typically used in shell scripts and batch programs to output status text to the screen or a file.

$ echo This is a test.
This is a test.
$ echo "This is a test." > ./test.txt
$ cat ./test.txt
This is a test.

Ping

echo refers to a ping request. See RFC 792.

Server

An echo server is a standard service that runs on TCP port 7. Intended for testing purposes, it replies to all packets with a packet containing the same data. It is rarely used in practice.