This cross teaches that Jesus Christ was victorious over death and through Him we can all conquer death
The letters IC XC are often accompanied with the letters NIKA.
Greek abbreviations are common among Eastern Christian iconography and in the West, on Italian panels.
On this cross IC represents the Greek characters Iota (Ι) and Sigma (Σ) - the first and last letters of Jesus (ΙΗΣΟΥΣ), and XC represents Chi (Χ) and Sigma (Σ) - the first and last letters of Christ (ΧΡΙΣΤΟΣ).
NIKA is taken from the Greek form of In Hoc Signo Vinces, meaning 'to be victorious' or 'to conquer'. Constantine adopted this motto when he witnessed the sign (see Chi Rho cross). The ICXC Cross is therefore also known as the Conqueror's Cross.
This cross teaches that Jesus Christ was victorious over death1 and through Him we can all conquer death2. (See The Meaning of the Cross).
1 Victory over death : Romans 6:4
2 Conquering death : Colossians 2:12