ping:

• Test network connectivity.

• Example: ping google.com

traceroute:

• Trace the path packets take to a destination.

• Example: traceroute example.com

nslookup:

• Query DNS servers.

• Example: nslookup google.com

netstat / ss:

• View network connections.

• Example: netstat -tuln or ss -tuln

curl and wget:

• Transfer data from or to a server.

• Example: curl http://example.com

• Example: wget http://example.com/file.zip