{newtxmath} sets a Times clone as the main math font. This tag can be used for questions about {newpxmath} as well.
newtxmath is part of the newtx bundle, that provides a replacement to txfonts. It splits txfonts into two independent packages: newtxtext and newtxmath, which allow to use a Times clone for the main text font and for the main math font, respectively.
newtxmath also provides options to use, instead of Times, one of the following fonts:
- Libertine
- StixTwoMath
- EBGaramond
- garamondx
- ScholaX
- MinionPro
- Baskervaldx
- Baskerville
- XCharter
- Cochineal
- Utopia
This tag can also be used for questions about the newpxmath package, which is part of the newpx bundle. newpx is very similar to newtx, but it allows to use Palatino clones instead of Times clones.
See the documentation of newtx and that of newpx for more information.