Dots at the end of names mean 'this is a fully qualified entry', without the dot, the DNS server appends the domain for which these entries are listed to the name. So, you would get foo1.bar.com.example.com
The full stops are critical therefore, to prevent errors.
All MX records have a priority. MX is a mail exchanger record, and you can have multiple MX entries per domain. The entry/entries tell mail servers where to send mail for your domain. The priority allows the mail server to try them in the right order (lowest first).
The first record says "if you look up this domain, you get this IP address", i.e. example.com gives x.x.x.x
The second is a wild card, which says, if you look up any sub-domain for this domain and there is no specific match, then you get this IP address. i.e. bob.example.com and fred.example.com will resolve, and they will resolve to that X.X.X.X.
TXT entries allow for informational records, of which yours is an SPF description. SPF is something else entirely, and handles e-mail validation, more info here - http://en.wikipedia.org/wiki/Sender_Policy_Framework.
The two NS entries are name server records, and tell other DNS servers/resolvers which name servers to use for your example.com domain.