In general, PBS offers following bidding options.
Off days: Bid the dates or weekdays off. It's the easiest and most popular bids.
Pairings: Bid specific pairing directly, it could be by pairing ID, or pairing ID on specific weekdays or on specific date.
Pairing Properties: These are the attributes of the pairings. They include report time between, release time between, connection time duration, layover time duration, layover cities, length of pairings, commutable pairings, standup pairings (CDO, Continuous Duty Overnight), sub-equipment type, average credit, deadhead preference, landing cities, and number of landings per duty, different base, etc.
Line Characteristics: These are the characteristics of the lines. They include average line credit, maximum day off, commutable work block, cadence, trip mix types, and work block size, off-day between work blocks. etc.
On Date General Bids: These offer some general bids on a specific date, such as report time between on specific date, release time between on specific date, pairing length on specific date and layover city on specific date.
Fly Avoid or Fly With: These offer the preferences to fly avoid ( such as check airman or a specific crewmember) or fly with specified crewmember.
Position: The position preference is for flight attendants such as service director, or different language positions.
Reserve: Bid preferred reserve off-days/properties or pre-built reserve hard lines and to bid as line holder or reserve alternatively. Or bid reserve duty dates in a combo line, a line contains both bid month pairings and reserve duties.
Pre-Built: Bid pre-built hard lines (such as true CDO lines).
In addition, most PBS's offer "Standing Bids". It's a collection of each crewmember's own general preference bids (such as weekdays off, pairing properties and line characteristics bids, etc.). These bids are not related to specific date. Each crewmember has his/her own standing bids defined by him/herself, which will be applied, as an option, if he/she did not submit any preference during the bidding session. Note: the concept of standing bids is not the same as "backup bids".
All PBS vendors offer similar bidding options, but the bidding methodology makes the huge difference. The bids you submit may not lead to the line you prefer.