Here is some code and query results to demonstrate - I created three entries, all for the site “domain.com” and three login usernames {LoginUser1, LoginUser2, LoginUser3}. Each item in the vault was labelled Alpha, Beta, and Gamma respectively:
(base) dh024:~$bw list items --search domain.com #return all three entries
? Master password: [hidden]
[{"object":"item","id":"ad865b54-4e74-4bab-911c-ad790142d7c2","organizationId":null,"folderId":null,"type":1,"name":"Alpha","notes":null,"favorite":false,"login":{"uris":[{"match":null,"uri":"domain.com"}],"username":"LoginUser1","password":"7%ZNDQru$rQikcS","totp":null,"passwordRevisionDate":null},"collectionIds":[],"revisionDate":"2021-08-03T20:08:05.373Z"},{"object":"item","id":"a2a20aa2-c26a-4b1f-9748-ad79014308b6","organizationId":null,"folderId":null,"type":1,"name":"Beta","notes":null,"favorite":false,"login":{"uris":[{"match":null,"uri":"domain.com"}],"username":"LoginUser2","password":"roVk6Sz!$onH#t4","totp":null,"passwordRevisionDate":null},"collectionIds":[],"revisionDate":"2021-08-03T20:08:16.516Z"},{"object":"item","id":"5fa78701-d6b5-471e-8b1b-ad79014347a5","organizationId":null,"folderId":null,"type":1,"name":"Gamma","notes":null,"favorite":false,"login":{"uris":[{"match":null,"uri":"domain.com"}],"username":"LoginUser3","password":"@6Ab%C01!5w%0Yj","totp":null,"passwordRevisionDate":null},"collectionIds":[],"revisionDate":"2021-08-03T20:09:06.636Z"}]
(base) dh024:~$bw list items --search LoginUser1 #return just one match
? Master password: [hidden]
[{"object":"item","id":"ad865b54-4e74-4bab-911c-ad790142d7c2","organizationId":null,"folderId":null,"type":1,"name":"Alpha","notes":null,"favorite":false,"login":{"uris":[{"match":null,"uri":"domain.com"}],"username":"LoginUser1","password":"7%ZNDQru$rQikcS","totp":null,"passwordRevisionDate":null},"collectionIds":[],"revisionDate":"2021-08-03T20:08:05.373Z"}]
(base) dh024:~$bw list items --search domain.com LoginUser1 #defaults to logical OR search; 3 matches
? Master password: [hidden]
[{"object":"item","id":"ad865b54-4e74-4bab-911c-ad790142d7c2","organizationId":null,"folderId":null,"type":1,"name":"Alpha","notes":null,"favorite":false,"login":{"uris":[{"match":null,"uri":"domain.com"}],"username":"LoginUser1","password":"7%ZNDQru$rQikcS","totp":null,"passwordRevisionDate":null},"collectionIds":[],"revisionDate":"2021-08-03T20:08:05.373Z"},{"object":"item","id":"a2a20aa2-c26a-4b1f-9748-ad79014308b6","organizationId":null,"folderId":null,"type":1,"name":"Beta","notes":null,"favorite":false,"login":{"uris":[{"match":null,"uri":"domain.com"}],"username":"LoginUser2","password":"roVk6Sz!$onH#t4","totp":null,"passwordRevisionDate":null},"collectionIds":[],"revisionDate":"2021-08-03T20:08:16.516Z"},{"object":"item","id":"5fa78701-d6b5-471e-8b1b-ad79014347a5","organizationId":null,"folderId":null,"type":1,"name":"Gamma","notes":null,"favorite":false,"login":{"uris":[{"match":null,"uri":"domain.com"}],"username":"LoginUser3","password":"@6Ab%C01!5w%0Yj","totp":null,"passwordRevisionDate":null},"collectionIds":[],"revisionDate":"2021-08-03T20:09:06.636Z"}]
(base) dh024:~$bw list items --search domain.com --search LoginUser1 #logical AND search; only 1 match
? Master password: [hidden]
[{"object":"item","id":"ad865b54-4e74-4bab-911c-ad790142d7c2","organizationId":null,"folderId":null,"type":1,"name":"Alpha","notes":null,"favorite":false,"login":{"uris":[{"match":null,"uri":"domain.com"}],"username":"LoginUser1","password":"7%ZNDQru$rQikcS","totp":null,"passwordRevisionDate":null},"collectionIds":[],"revisionDate":"2021-08-03T20:08:05.373Z"}]
(base) dh024:~$bw list items --search domain.com --search Beta #another logical AND search; 1 match
? Master password: [hidden]
[{"object":"item","id":"a2a20aa2-c26a-4b1f-9748-ad79014308b6","organizationId":null,"folderId":null,"type":1,"name":"Beta","notes":null,"favorite":false,"login":{"uris":[{"match":null,"uri":"domain.com"}],"username":"LoginUser2","password":"roVk6Sz!$onH#t4","totp":null,"passwordRevisionDate":null},"collectionIds":[],"revisionDate":"2021-08-03T20:08:16.516Z"}]
(base) dh024:~$bw list items --search LoginUser --search Gamma #another logical AND; 1 match
? Master password: [hidden]
[{"object":"item","id":"5fa78701-d6b5-471e-8b1b-ad79014347a5","organizationId":null,"folderId":null,"type":1,"name":"Gamma","notes":null,"favorite":false,"login":{"uris":[{"match":null,"uri":"domain.com"}],"username":"LoginUser3","password":"@6Ab%C01!5w%0Yj","totp":null,"passwordRevisionDate":null},"collectionIds":[],"revisionDate":"2021-08-03T20:09:06.636Z"}]