Here is a list of all namespaces with brief descriptions:

[detail level 123]

▼Nankerl
▼Nnanobench
Ndetail
Ntemplates
NBCLog
Nbech32
▼Nbenchmark
Ndata
▼Ncapnp
Nschemas
Ncommon
NConsensus	Transaction validation functions
NCuckooCache	High-performance cache primitives
Ndbwrapper_private	These should be considered an implementation detail of the specific database
Nfs	Filesystem operations and types
Nfsbridge	Bridge operations to C stdio
NGUIUtil	Utility functions used by the Bitcoin Qt UI
▼Ni2p
Nsam
Ninit
Ninterfaces
▼Nipc
▼Ncapnp
Nmessages
Njson_tests
Nkernel
Nmemusage
Nminer_tests
▼Nminiscript
Ninternal
▼Nmp
Necho_fields
Ninit_fields
NNetMsgType	Bitcoin protocol message types
Nnode
▼Norg
▼Nbitcoincore
Nqt
Npoly1305_donna
Npyminisketch
Nripemd160	Internal RIPEMD-160 implementation
NRPCServer
Nsha1	Internal SHA-1 implementation
Nsha256	Internal SHA-256 implementation
Nsha256_arm_shani
Nsha256_implementation
Nsha256_x86_shani
Nsha256d64_arm_shani
Nsha256d64_avx2
Nsha256d64_sse41
Nsha256d64_x86_shani
Nsha512	Internal SHA-512 implementation
Nspanparsing
Nstd
Ntests_wycheproof_generate
▼Ntinyformat
Ndetail
Ntorv3
NUi
Nutil
Nvalidation_block_tests
▼Nwallet
NDBKeys
Nfeebumper
Nwallet_crypto_tests
NWalletTool