Why was this terminology of holomorphism used here?

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page 6 in this notesays:

A note on index convention: $i$,$j$, and $\bar{i}$, $\bar{j}$ index over the holomorphic and antiholomorphic components.

I never knew there were holomorphic components, I only was aware of holomorphic mappings and holomorphic functions. Can someone please point out why was this terminology used here?