First we need to know what “ls” means - ls *.c “ls” is a command to list computer files and directories on Unix and Unix-like operating systems, with no option, the “ls” lists files and directories in the current folder, so we can see all of his content. The “*.c” provides more information for the ls command
The “*” is a wildcard, it select all the content of the current directory, so when we add “.c” to the wildcar, it works for searching all the content whit “.c” extension, including all matches like folder.c or file1.c