Calls have delta from 0 to 1; puts from 0 to -1. A 0.30-delta call gains about $0.30 when the stock rises $1 and is roughly 30% likely to finish in-the-money. Delta itself changes as the stock moves, which is what gamma measures.
Position delta (sum of deltas times contracts times 100) tells you your stock-equivalent exposure.
Example: you own 4 calls with 0.45 delta. Position delta is 4 x 0.45 x 100 = 180 shares equivalent. A $2 stock rise gains about $360.
Related: gamma, theta, vega, in-the-money, hedge