Apache Kafka's Streams API provides various join types for stateful and stateless streams, including inner joins, left joins, outer joins, KTable-KTable joins, stream-table joins, and KStream-GlobalKTable joins. These joins can be used to combine data from multiple sources, such as combining view events with click events in an online advertising domain. The join semantics differ from SQL semantics and have runtime dependencies on processing order or timestamp synchronization. The Streams API also supports changelog streams, tombstone messages for deletes, and global tables that hold a complete copy of all data over all partitions of their input topic. The choice of join type depends on the specific use case and requirements, such as stateful vs. stateless processing, windowing, and partitioning constraints.