Bech32 is a segwit address format specified by BIP 0173. While this address format has been included in some implementations, as of December 2017, the address format is not recommended for use until more software supports the format.
Examples of the address format being used on mainnet are the TXIDs
514a33f1d46179b89e1fea7bbb07b682ab14083a276979f91038369d1a8d689b. And addresses
- Talk by Pieter Wuille the new bech32 address format (March 2017) https://www.reddit.com/r/Bitcoin/comments/62fydd/pieter_wuille_lecture_on_new_bech32_address_format/
- Comment by maaku7 explaining how bech32 addresses improve the security of (for example) multisignature https://www.reddit.com/r/Bitcoin/comments/74tonn/bech32_native_segwit_address_already_used_on_the/dqlogru/