You can now get to Sunderland direct from London and York via Grand Central Trains although there is only approx. 3 services a day otherwise you have to travel to Newcastle Central Station and change to the Tyne and Wear Metro.
The bus service is quite good during the day but can be poor at night and operates via Sunderland Interchange which also has Park Lane Metro Station. The Metro goes only to South Hylton (a village on the outskirts with nothing of real note) or Newcastle-upon-Tyne but can connect to other metro line for Newcastle Airport or Whitley Bay and the coast.
There is a variety of bus, rail and metro tickets, but if you're travelling solely in Tyne and Wear there is daily, weekly tickets that cover most forms of transport (Most buses, the metro, rail services between Metrocentre - Newcastle - Sunderland and the North Shields - South Shields Ferry)
To get there, you have to go via Newcastle - despite there being provision to do so, there is no direct train link from London (a direct train via Hartlepool, Stockton and York would be possible), though strangely there is from Liverpool, Manchester, Leeds or York. Bar these places, you have to travel to Newcastle Central Station and change to the Tyne and Wear Metro.
Newcastle Airport is the nearest and not best provided - the much promised direct filght to North America has never appeared - and really only serves locals heading around the UK (London, Bristol, Aberdeen, Dublin, Southampton, etc) or Europe (Paris, Brussels, Scandinavia, etc.), or heading for the Mediterranean beach resorts on charter flights. To get to Sunderland from here, you either have to get a taxi at very high rates or use the Metro to get to Newcastle, change trains, then continue on a second Metro to Sunderland - when you change, no need to find another platform. Strangely, Nexus, the local transport authority, decided not to bother with a direct Metro link - again perfectly possible.
Buses okay during the day, but few and far between on the nightime. The Metro goes only to South Hylton (a village on the outskirts with nothing of real note) or Newcastle-upon-Tyne and basically designed to take people out of Sunderland to Newcastle, not to help people get around Sunderland, which it completely fails to do.