Source

File: wp-admin/includes/class-wp-themes-list-table.php

public function search_theme( $theme ) {
		// Search the features.
		foreach ( $this->features as $word ) {
			if ( ! in_array( $word, $theme->get( 'Tags' ), true ) ) {
				return false;
			}
		}

		// Match all phrases.
		foreach ( $this->search_terms as $word ) {
			if ( in_array( $word, $theme->get( 'Tags' ), true ) ) {
				continue;
			}

			foreach ( array( 'Name', 'Description', 'Author', 'AuthorURI' ) as $header ) {
				// Don't mark up; Do translate.
				if ( false !== stripos( strip_tags( $theme->display( $header, false, true ) ), $word ) ) {
					continue 2;
				}
			}

			if ( false !== stripos( $theme->get_stylesheet(), $word ) ) {
				continue;
			}

			if ( false !== stripos( $theme->get_template(), $word ) ) {
				continue;
			}

			return false;
		}

		return true;
	}