A 20-day moving average is...

The average of the last 20 daily closes

Moving averages | TradeLiga

Charts are noisy. A moving average (MA) smooths them: it's the average closing price of the last few candles, drawn as a line.
A 20-day MA adds up the last 20 daily closes and divides by 20. Tomorrow the oldest day drops out and the newest joins. That's why it “moves”.
Price above a rising MA suggests an uptrend. Price below a falling MA suggests a downtrend. Price weaving around a flat MA: no clear trend.
Fast vs slow: a 20-period MA hugs price and reacts quickly. A 200-period MA moves slowly and shows the long-term direction.
When the 50-day MA crosses above the 200-day, traders call it a golden cross. The opposite is a death cross. Headlines love them.
Common mistake
Mistake: expecting an MA to predict turns. It's built from past prices, so it always lags. It confirms trends; it doesn't call tops or bottoms.
Key takeaway
A moving average is a smoothing tool: use it to see the direction, not to predict the future.

A 20-day moving average is... The average of the last 20 daily closesAdd the last 20 closing prices, divide by 20, and redraw it every day.
Price is above a rising average. That suggests... An uptrendRecent prices are above the average and the average itself is climbing.
The main weakness of moving averages is that they... Lag behind priceThey're built from past closes, so they react after price has already moved.
Which reacts faster to new prices? A 20-period MAFewer candles in the average means each new price has a bigger effect.