From Pentecost to the first Sunday of Advent is the liturgical season called ordinary time. The description below is what I consider the most important part of the description taken from Wikipedia, specifically from https://en.wikipedia.org/wiki/Ordinary_Time.
Ordinary Time (Latin: Tempus per annum) is the part of the liturgical year in the liturgy of the Roman Rite, which falls outside the two great seasons of Christmastide and Eastertide, or their respective preparatory seasons of Advent and Lent. Ordinary Time thus includes the days between Christmastide and Lent, and between Eastertide and Advent. The liturgical color assigned to Ordinary Time is green. The last Sunday of Ordinary Time is the Solemnity of Christ the King.
The word “ordinary” as used here comes from the ordinal numerals by which the weeks are identified or counted, from the 1st week of Ordinary Time in January to the 34th week that begins toward the end of November
Specifically for the Roman Rite:
In the ordinary form of the Roman Rite, the Feast of the Baptism of the Lord, which ordinarily occurs on the Sunday after the Solemnity of the Epiphany of the Lord (6 January), begins Ordinary Time and closes the Season of Christmas. The weekdays that follow the Feast of the Baptism of the Lord are reckoned as belonging to the first week of Ordinary Time which continues until the Tuesday that immediately precedes Ash Wednesday.
After Eastertide the Ordinary Time resumes on the Monday after the Solemnity of Pentecost. In regional calendars where Whitmonday is a Day of Obligation, Ordinary Time and the use of the liturgical colour Green may begin on the following Tuesday.
Traditional Thomistic Catholic 