Different between dynamic IP and statis IP is that, dynamic IP may changed after you restart your PC, while statis IP won't change. Dynamic IP is assigned to you by DHCP at modem, and usually your IP will be the same if no one else took your IP. When I stay at hostel, there's so many students sharing same internet, so bad that DHCP can't assign empty IP for me and other students. We have to type in static IP, and we need to try a lot of times for that. Why? Let me explain.
As an example, see picture embedded. I have set my IP to be static. My static IP is 192.168.1.103. The 103 is a unique number for me, so the person who share internet with me have to take other number. They will have to use 192.168.1.1, or 192.168.1.2 ... until limit at 192.168.1.254. This means that there's a maximum of 255 people can share the same modem, but there's very rare that this will happen for normal use.
IP address 192.168.1.x is given by ISP, and you need refer your modem for that. Different modem may have different numbers.
Below IP address is Subnet mask. It normally is 255.255.255.0, by which your PC will auto fill in for you.
Default gateway is the node to connect to the internet. It provides an entry point and an exit point in a network. It's provided by ISP, and it's "the number that connect to internet". When you type http://
DNS server is a server to help you find a website. For example you type www.google.com. Internet won't understand, because it's in abc. Also, google website is in numbers too. Try run "ping www.google.com" and you will get numbers instead of abc. DNS help to to access to google by changing www.google.com to 22.214.171.124 . You can always type 126.96.36.199 in address bar to access google, but you will have problem to remember those numbers. So DNS help you to access the page without the need for you to remember them.
My first choice DNS server is 192.168.1.1, which given by my ISP. It has lowest ping, thus will 'decrypt' faster for me, thus increase my browsing rate. My second choice is 188.8.131.52, which is a google DNS server. It's quite low ping for me too. You can run a test to determine best DNS for you here.