Open the Search Terms tab in Google Ads. It shows the actual terms people searched that triggered your ads in the selected period, with spend, impressions, clicks, CTR, CPC, conversions, CPA and ROAS for each term, plus a search field to filter. Each row has two buttons: the plus button (green) adds the term as a keyword in an ad group and lets you choose the match type (Exact, Phrase or Broad); the minus button (red) adds the term as a negative keyword. When adding a negative, you choose the match type and the level: Campaign (blocks it across the whole campaign) or Ad Group. It's one of the most efficient routines for cutting spend on irrelevant searches.

Shared negative keyword lists are also here: the Negative Lists button inside the Search Terms tab.