A greedy quantifier such as .* consumes as much as possible while still allowing the rest of the pattern to match. In <b>one</b><b>two</b>, the pattern <b>.*</b> can span both elements. Changing it to <b>.*?</b> makes the repetition lazy, so it stops at the first possible closing tag.
Lazy is not automatically robust. A more specific pattern such as <b>[^<]*</b> can fit a narrow example, but regular expressions are a poor substitute for an HTML parser when nesting, attributes, or malformed markup matter. In the Regex Tester, include two adjacent matches, a missing delimiter, and a newline to see what the pattern actually accepts. Test the exact regex engine used by your application.
One practical rule I use: when the closing delimiter is known, prefer a negated character class over a broad wildcard. <[^>]*> states the boundary directly; <.*?> merely asks the engine to stop early. Neither should be used as a full HTML parser, but for constrained snippets the first pattern is clearer and usually less prone to surprising backtracking. Always test malformed and missing-delimiter cases, not only the happy path.
Akousa