What does "all who call on the name of the Lord shall be saved" (Romans 10:13) mean?

Rom 10:13 For whosoever shall call upon the name of the Lord shall be saved.

For

This passage quotes Joel 2:32 and attributes it to the Lord Jesus. The exaltation of Christ through His resurrection exemplifies His sovereignty in offering salvation; He extends it to everyone. Salvation is attainable solely through Him. This serves as scriptural evidence of God's all-encompassing mercy.

whosoever shall call

The word “whoever” is understood as (Greek—“all”). Salvation is available to all.

Here, "calls" signify a petition of need; it represents a self-humbling before the LORD. We are insufficient to meet the criteria for salvation. In this context, calling is tantamount to believing in all that God has pledged to us. We rely on His nature to fulfill His promises.

Acts 2:21, And it shall come to pass, that whosoever shall call on the name of the Lord shall be saved.

upon the name of the Lord

The “name of the LORD” is His identity; it is the LORD Himself. Jesus is the Creator and sovereign (Acts 17:31; Hebrews 1:2). All the riches God has for us are encapsulated in His "name," representing all that He is. We can place our current circumstances and our eternal destiny in the security of that name.

Prov 18:10 The name of the LORD is a strong tower: the righteous runneth into it, and is safe.

To call on the name of the Lord signifies a belief in all that His name represents; it means understanding the Lord in His qualities as the Savior and Lord of all, thereby approaching Him by His grace.

shall be saved

The term "saved" evokes thoughts of our everlasting future with the Lord. The Greek indicates that salvation is received (in the passive voice), rather than achieved through our actions. Believers are recipients of God's salvific work. Salvation hinges on the identity and work of Jesus Christ.