Meaning: This sentence tells us that a group of people moved from one place to another, specifically to a public area with trees, grass, and other recreational facilities.
Choice of Words: The word "they" refers to a group of people. "Went" is a verb that indicates movement from one place to another. "To" indicates the direction of movement. "The" is a definite article. "Park" refers to a public area with trees, grass, and other recreational facilities.