So a currency can both inflate and deflate at the same time?
The meanings of "inflation" and "deflation" are ambiguous.
In economics, "inflation" is an increasing money supply. It may or may not result in increasing prices. In layman's terms, "inflation" means increasing prices of goods, which may or may not be caused by an increasing money supply. "Deflation" is the same, except opposite.
In economic terms, Bitcoin is currently
inflationary because its money supply is increasing. When no more bitcoins are mined, then Bitcoin becomes
deflationary because its money supply can only decrease as bitcoins are lost.
In layman's terms, bitcoin is currently (and probably will always be)
deflationary, because the demand for bitcoins is increasing much faster than the supply, and as the value of a bitcoin increases, the prices of goods decrease.