Minecraft wiki entry for Illager, associated text: Patrol — a naturally spawned group of five pillagers roaming the landscape and monitoring the villages.
Raid — waves of illagers and witches spawn and attack a village with ominous horn blares. in Java Edition, An illager captain spawns in each wave with other illagers, usually with a vindicator as the captain. It is triggered when a player with the Bad Omen status effect enters a village. Raiders and villagers usually have different behavior in a raid. In Bedrock Edition, any killed raiders drops special loot. Raiders celebrate after defeating a village.