Portugal is a catholic country (above 80% of the population is catholic). The Holy week (or, as the Portuguese call it: Semana Santa is celebrated with just devotion and has a predominantly religious character. Although it is less intensive than in Spain, you will still find traditional festivities in the Algarve that are fascinating to attend.
It all starts forty days before Easter, when the period of soberness and fasting is begun and many people abstain from eating meat. Easter Sunday 2019 is 21 April.