Prōtotokos (G4416) means firstborn — the first child born of a mother, and by extension, the one who holds the rights and preeminence of the firstborn. It combines prōtos ('first') and tikto ('to give birth'). It appears 8 times in the New Testament. In Jewish culture, the firstborn held a position of supreme honor, double inheritance, and covenant significance. The term carries both temporal priority (born first) and positional preeminence (chief, supreme).
Prōtotokos is a major christological title. Colossians 1:15 calls Jesus 'the firstborn of all creation' — a statement of supreme preeminence over all created things (not that he was a creature, as the context of vv. 16-17 clarifies: 'in him all things were created... he is before all things'). Paul draws on the OT theology of firstborn: the firstborn is the image of the father, the heir of the estate, the representative of the family.
Colossians 1:18 adds: 'the firstborn from the dead' — he is the first to be raised in the new resurrection body, and his resurrection is the pattern and guarantee of ours (cf. 1 Corinthians 15:20, aparchē tōn kekoimēmenōn, 'firstfruits of those who have fallen asleep'). Romans 8:29 says God predestined believers to be 'conformed to the image of his Son, in order that he might be the firstborn among many brothers' — Jesus is the eldest brother of a family being created through grace.