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Using a set of administrative policies BGP speakers within the AS come to an agreement as to which entry/exit point to use for a particular destination. This information is communicated to the interior routers of the AS using the interior routing protocol (IGP), for example, OSPF, RIP, or static routing. In certain setups, iBGP can take the IGP protocol role as well.
For certain BGP attributes handling behavior may change depending on what type of connection is set up, for example, the LOCAL-PREF attribute is not advertised to eBGP peers.
Let's look at a very basic eBGP configuration example assuming, that Router1 IP is 192.168.1.1, AS 65531 and Router2 IP 192.168.1.2, AS 65532:
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