Lent lasts 40 days (beginning on Ash Wednesday and ending at sundown on Holy Thursday, excluding Sundays).
The three pillars of Lent are prayer, fasting, and almsgiving.
Ash Wednesday and Good Friday are days of fasting (see requirements here) and abstinence from meat.
All Fridays in Lent are days of abstinence from meat.
During these 40 days, we are in the desert with Jesus, inviting God to work in us during this time of sacrifice as we prepare to renew our baptismal promises at Easter.