Archways connecting what historically were two separate stations.
Historically the London Brighton & South Coast Railway, also known as the Brighton Line.
Victoria Station actually is historically two stations immediately next to each other. After the 1923 consolidation into Southern Railway, archways were cut in the walls between the two stations, forming one common station area between the street entrances and the platform gates. A common platform numbering system was adopted, with Platforms 1-8 on the Chatham side and Platforms 9-19 on the Brighton side. Outside the station, minimal track connections exist between the two sets of tracks.
MAIN LINE: Victoria-Brighton
4 tracks Victoria-Three Bridges, 2 tracks beyond
From east to west, pairs of tracks identified as Slow, Fast (north of Purley).
From east to west, pairs of tracks identified as Fast, Slow (south of Earlswood).
Between Purley and Earlswood, Slow and Fast lines are separate, identified as Redhill Line, and Quarry Line which bypasses Redhill. Quarry Line passes over Redhill Line between Coulsdon South and Merstham.
Crystal Palace (Balham-Beckenham)
Arun Valley (Three Bridges-Horsham-Arundel)
Uckfield (1 track/diesel)
Tonbridge (from Redhill)
North Downs (west of Redhill/diesel)
Lewes (from Wivelsfield)
East Coastway (Brighton-Hastings)
Rye (Hastings-Ashford/diesel/1 track)
West Coastway (Brighton-Havant)
All lines 2 tracks unless noted. All lines DC electrification unless noted.
Number Of Platforms/Tracks: 11
Platforms numbered east to west
Platform 9-12 - Slow Line
Platform 13-14 - Fast Line/Gatwick Express
Platform 15-19 - Fast Line
Wikipedia link containing further station information and history.
Zoomable Google Maps along the various lines.