I can't understand what causes there errors - node.js

Question

After installing packages using npm install webpack webpack-cli webpack-dev-server --save-dev
The terminal gives me this error message:
➜ Projeto npm install webpack webpack-cli webpack-dev-server --save-dev
npm WARN deprecated chokidar#2.1.8: Chokidar 2 will break on node v14+. Upgrade to chokidar 3 with 15x less dependencies.
npm WARN deprecated fsevents#1.2.13: fsevents 1 will break on node v14+ and could be using insecure binaries. Upgrade to fsevents 2.
npm WARN deprecated resolve-url#0.2.1: https://github.com/lydell/resolve-url#deprecated
npm WARN deprecated urix#0.1.0: Please see https://github.com/lydell/urix#deprecated
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents#^1.2.7 (node_modules/chokidar/node_modules/fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents#1.2.13: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})
npm WARN projeto#1.0.0 No description
npm WARN projeto#1.0.0 No repository field.
+ webpack-dev-server#3.11.2
+ webpack-cli#4.7.0
+ webpack#5.38.1
updated 3 packages and audited 499 packages in 35.305s
1 package is looking for funding
run `npm fund` for details
found 1 moderate severity vulnerability
run `npm audit fix` to fix them, or `npm audit` for details
➜ Projeto material-ui
zsh: command not found: material-ui
➜ Projeto npm install # material-ui / core
npm WARN deprecated material-ui#0.20.2: You can now upgrade to #material-ui/core
npm ERR! code EINVALIDTAGNAME
npm ERR! Invalid tag name "#": Tags may not have any characters that encodeURIComponent encodes.
npm ERR! A complete log of this run can be found in:
npm ERR! /home/peter/.npm/_logs/2021-06-02T04_35_32_632Z-debug.log

Answer 1

Because you typed
npm install # material-ui / core
instead of
npm install #material-ui/core
npm went and tried to install the packages #, material-ui, / and core. Because # on its own is an invalid tag name, it threw that error. To undo what you've done, you need to execute:
npm uninstall material-ui core
and then
npm install #material-ui/core --save-dev