What is an MT4 indicator?
An indicator simply manipulates price data using a mathematical formula. The indicator shows a visual representation of the mathematical formula and price inputs. To a skilled chart reader or trader an indicator often won't reveal more than what is visible just by analyzing the price chart (or volume) without any indicators.
That said, since there is so much to be analyzed on a price chart an indicator helps simplify it. This is why indicators are so alluring to new traders. Instead of learning to how to identify a trend on the price chart, they try to find an indicator that will identify the trend and trend reversals for them.
Indicator based trading is relying on indicators to analyze the price and provide trade signals. Many indicators provide a specific trade signal which alerts the trade that now is the time to take a trade.
Many people view indicator based trading as easier than price action trading, because indicators appear simple. Easier doesn't mean more profitable though. Understand any indicator you use, and what its strengths and weaknesses are. For new traders indicators help spot opportunities (to get in or out of a trade) which may not be visible to them on the price chart. For the most part though, many indicators only tell you what the price chart is telling you. Therefore, use indicators if needed, but if they aren't actually increasing your profit at all, then question why you are using them.