Incoming links are links from websites that have links pointing to your website. Outgoing links (also known as "outbound links") are links on your own site which connect to other sites i.e. links that will lead your visitors away from your own site.
The link coming from other site to your site is inbound links and the link you are placing at your site for other site is outbound link.
It's really simple the links which are live on your site but point to some other site are called external or outbound links But the links which exist on other sites and point to your site are called internal or Inbound link...