Technical indicators in trading can be categorized into several types, each serving a specific analytical purpose. Here are some common types of technical indicators:

• Trend-following Indicators: These help identify the direction and strength of a market trend and include the likes of moving averages, Moving Average Convergence Divergence (MACD), Parabolic SAR, and Average Directional Index (ADX)
• Momentum Indicators: These gauge the speed and strength of price movements and include the likes of the Relative Strength Index (RSI), Stochastic Oscillators, and the Commodity Channel Index (CCI)
• Volatility Indicators: These measure the degree of price variability and include Bollinger Bands, Average True Range (ATR), and the Volatility Index (VIX)
• Volume Indicators: These analyze trading volume alongside price movements and include the likes of the On-Balance Volume (OBV), and the Money Flow Index
• Support and Resistance Indicators: These highlight key price levels and include the likes of Pivot Points, Ichimoku Cloud, and Fibonacci Retracement Levels
• Chart Patterns: These are visual patterns that can signal potential price movements and include the likes of Head and Shoulders, Triangles, Flags and Pennants

Technical indicators are versatile tools that allow traders to analyze the markets and identify support and resistance levels to enter the market at favorable times. 

However, it must be noted that the use of too many indicators can overcomplicate the chart and lead to much more confusion than clarity.

Technical Indicator Example - MACD

To better understand how technical indicators work on a chart, we can look at an example of an indicator, such as the MACD plotted against the price chart of Apple Inc stock (AAPL):

The MACD shows the momentum of the price of Apple shares, which can show favorable entry points on the price chart. 

The difference between the MACD line and the signal line is plotted as a histogram, which is plotted below the price chart. 

When the MACD line crosses above the signal line, the histogram is positive, indicating potential bullish momentum.

Conversely, when the MACD line crosses below the signal line, the histogram is negative, suggesting potential bearish momentum.

Furthermore, crossovers between the MACD line and the signal line can signal a potential reversal in the price trend.

Technical indicators are useful to traders in a myriad of ways, such as: Trend identification and confirmation, assessment of momentum on the market, visualization of data, and more. 

Indicators like RSI signal when an asset may be overbought (potential sell) or oversold (potential buy).

On the other hand, indicators like RSI and MACD gauge the strength and speed of price movements.

Traders use indicators to pinpoint optimal entry and exit levels for trades, which makes them very useful to traders. 

• Technical indicators are tools used by traders to identify and confirm trends on the market by plotting the indicator line on or below the price chart
• Various indicators provide buy and sell signals based on a variety of data, such as volume, volatility, support and resistance levels, etc 
• Indicators are also used to measure trend strength for traders to understand whether a reversal is likely to occur 
• By using technical indicators, traders can identify potentially profitable trades. However, overusing indicators can overcomplicate the chart and make it more difficult to gauge accurate information