Two places, two types of information

When you add an indicator your platform puts it in one of two places, and that placement is telling you something.

Overlays are drawn on the price chart, in price units. Moving averages, Bollinger Bands, SuperTrend, Ichimoku, VWAP. Because they are measured in the same units as price, you can compare them to price directly: is price above or below the average, is it touching the upper band, how far in dollars is it from the VWAP.
Oscillators live in a separate pane below, in their own units. RSI, Stochastic, MACD, CCI, Williams %R. Their values are not dollars — they are ratios, percentages or index numbers. You can never ask "how far above the RSI is price", because the question makes no sense.

What follows from that

An overlay can be read against price: distance, position, touches, crosses. That makes overlays natural for support and resistance, for trailing stops, and for "how stretched is this move in actual dollars".

An oscillator can only be read against its own history or its own thresholds. RSI at 68 means the momentum ratio is at the high end of its recent range — full stop. It does not mean price is 68, or 68% of anything. This is why beginners who try to use oscillators as levels on the price chart end up confused: the two panes have different y-axes and there is no meaningful distance between them.

Bounded and unbounded

One more distinction worth knowing. Some oscillators are bounded — RSI lives between 0 and 100, Stochastic between 0 and 100, Williams %R between -100 and 0. Because they have fixed edges, people draw threshold lines on them (70/30, 80/20). Others are unbounded: MACD has no upper or lower limit, so its absolute value means nothing without context — you read the relationship between its lines, not the level.

Reading a bounded oscillator's level as if it were absolute, or an unbounded one's level as if it had thresholds, is one of the most common ways to misread an indicator.

How to check this yourself

Add a 20-period Bollinger Band (overlay) and RSI(14) (pane). Note the y-axis on each. Then ask one question of each: "how many dollars is price from the upper band?" — answerable for the bands, meaningless for RSI. "Is momentum at an extreme for this month?" — answerable for RSI, meaningless for the bands. Being clear about which question belongs to which pane prevents a lot of nonsense setups.