What does Psalm 50:2 mean?

This passage introduces God using a three-part description of His power and authority. Along with that description, everything in creation is commanded to attend His words (Psalm 50:1). His glory emanates from His chosen location; in this case, it is the temple on Mount Zion in Jerusalem.

Zion is an alternate name for Jerusalem, the "city of God." It was originally a Canaanite city, but David claimed it and moved the ark of the covenant there (2 Samuel 6:12–15). Later Zion was referred to as the temple and the holy hill (Psalms 3:4; 15:1), "the hill of the Lᴏʀᴅ" (Psalm 24:3), and "[God's] holy mountain" (Zephaniah 3:11). Psalm 78:68 states emphatically that the Lord loves Mount Zion (cf. Psalm 87:1–2). Much of Jerusalem's praise in Scripture comes from its status as the de-facto capital city of God's chosen people (Ecclesiastes 1:12). Mostly, however, Zion is applauded as the location of the temple (Psalm 2:6; 48:2; 68:29; 132:13; Joel 3:17; Zechariah 8:3). This was the site of God's "presence" on earth during the Old Testament period (Psalm 11:4; Habakkuk 2:20).