Samba is a collection of programs for Linux (as well as other Unix-like OSs) to allow them to use the Windows file sharing (SMB) protocol.
smbclient is the client program. You can use the Linux smbclient program to access files on other computers (typically Windows machines, but could be Linux or Mac computers running Samba server) that are shared through SMB.
If you want to host Windows file sharing (SMB) shares on your Linux machine, then you need to set up the Samba server. That way, other computers (whether Windows, Mac, or Linux) can access your files through SMB.