411 REFERENCE · Wikibooks
Chess Opening Theory/1. e4/1...c5/2. Nf3/2...d5
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Sicilian defence B27 Sicilian defence → 2. Nf3
2...d5?
A move that has some popularity with beginners only, who want to open the centre immediately.
Something like a delayed Scandinavian defence, the forcing sequence is 3. exd5 Qxd5 4. Nc3 (White gains time on Black's queen). Unable to move to a5, as the main line of the Scandinavian, the queen returns to 4...Qd8.
Black has lost time and White is ahead in developing their minor pieces. Black has half-opened their d-file, so White should play 5. d4, or they will find it difficult to later: 5. Bc4? Nc6 and Black controls d4 three times to White's twice.