target is pretty self explanatory, it determines which version your final JS code will be compiled down to.
lib basically tells TS what features not to complain about
By default, when you specify a target, the default lib includes that target and dom
lib specifies a set of bundled library declaration files that describe the target runtime environment.
--lib Specify a set of bundled library declaration files that describe the target runtime environment.
one or more: es5, es6, es2015, es7, es2016, es2017, es2018, es2019, es2020, es2021, esnext, dom, dom.iterable, webworker, webworker.importscripts, webworker.iterable, scripthost, es2015.core, es2015.collection, es2015.generator, es 2015.iterable, es2015.promise, es2015.proxy, es2015.reflect, es2015.symbol, es2015.symbol.wellknown, es2016.a rray.include, es2017.object, es2017.sharedmemory, es2017.string, es2017.intl, es2017.typedarrays, es2018.asyn cgenerator, es2018.asynciterable, es2018.intl, es2018.promise, es2018.regexp, es2019.array, es2019.object, es 2019.string, es2019.symbol, es2020.bigint, es2020.promise, es2020.sharedmemory, es2020.string, es2020.symbol. wellknown, es2020.intl, es2021.promise, es2021.string, es2021.weakref, esnext.array, esnext.symbol, esnext.as ynciterable, esnext.intl, esnext.bigint, esnext.string, esnext.promise, esnext.weakref
lib does NOT include any polyfills. If you add ESNext, it’ll not mean that TypeScript will compile down your TS code written in ESNext to your ES2015 or whatever target. It will mean that you’re kina sorta promising TS that these libs will be supported, so don’t complain about it.
For example, if my target is ES2015, specifying ESNext as lib will NOT convert .includes() to ES2015 code.
Remember, TS never injects polyfills in your code.
.
You want polyfills you need to add those yourself
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So in short: configure
targetfirst, and if you need any extra polyfill in your project OR you know your browser(s) will support this little extra feature,libis how to make TS happy about it.