I am new to ubuntu server as well as server too.
When I am checking the open port using command 'netstat' .On the column of local address, there is *.http and *:ssh
what does * meaning of?
It means that services http and ssh are listening on all addresses available on your server.
This means at least listening on localhost (127.0.0.1) and probably on the LAN address (eg: 10.x.x.x or 192.168.x.x).
The asterix indicates that the service is listening for traffic on ALL available addresses.
Localhost and the machines defined ip-address.
If a service is only bound to a specific ip-address you will see that listed here by address.
Please note this also includes services listing for multicast addresses. (So you will see 224.0.0.* appear as an ip-address in some cases.)