The bread, or what remained after the offering portion was burned, was for the sustenance of the priests. There were a number of different offerings for which a portion was given to the priest, either to consume within the holy place, or to share with those in his household.
Both of these point to an important consideration still at work in our churches today. Spiritual ministry requires physical maintenance. Whether it is providing for people's physical hunger before offering to satisfy their spiritual hunger, providing the resources for the church's lights to stay on, or providing for those who serve the body of Christ and their families, this principle is essential. There are certainly plenty of examples where this has either been neglected or abused - neglect would be the pastor whose family goes without or the church building lacking in necessary maintenance. Abuse would be those who fleece their flock to live in luxury. The example God sets is one of balance, where needs are met well without gluttony or greed and without creating hardship on those tasked to provide.
This is a short chapter - with a lot more meat than I can do justice to - if you'd like to dig deeper, I've included the link for the commentary I read on Bible.org.
Note: I found an interesting commentary on this chapter titled, "The Lamp, the Loaves, and the Loudmouth" - great title. https://bible.org/seriespage/18-lamp-loaves-and-loudmouth-leviticus-24