God is generous with His grace. One need only acknowledge that forgiveness comes from God to get it. There are no moral requirements. There are no mental requirements. There is no call to a certain denomination. In this sense, Christianity is incredibly inclusive. All people are welcome. No one who comes will be turned away.
But people cannot believe in whom they do not know. Here is the need for missions. The clear implication is that apart from this God, there is no salvation. In this sense Christianity is very exclusive. There is only one way to God: faith in Jesus Christ.
The Dr. Dale Brunner, a Presbyterian minister uses the cross to illustrate this. The arms of the cross represent the inclusiveness of the invitation. And the vertical bar represents the exclusiveness of the way to take advantage of the invitation. Christianity is both inclusive and exclusive.