Elliott Wave Theory, developed by Ralph Nelson Elliott , proposes that the seemingly chaotic behaviour of the different financial markets isn’t actually chaotic. In fact the markets moves in predictable, repetitive cycles or waves and can be measured and forecast using Fibonacci numbers.

The very basics of Elliott Wave Theory;
The Elliott wave principle at its core consists of motive waves, movement in the direction of the larger trend, and corrective waves, any correction against the main trend. Market prices alternate between a motive phase, and a corrective phase on all time scales of trend.
Wave analysis offers insights into trend dynamics and helps you understand price movements in a much deeper way and offers the trader a level of anticipation and/or prediction when searching for trading opportunities

Motive Waves
Motive waves in general can be categorized as Impulse and Diagonal waves

a- Impulse Waves
Impulse waves consist of five sub-waves in the same direction as the trend of one larger degree.

Elliott proposed that financial price trends, the waves, are created by investor psychology or sentiment and the waves can be measured and forecast using Fibonacci numbers. In adition to using fibonacci retracments and extetion to forcast probable targets, channeling technique is also presented, where channeling technique is used to forecast wave formations and targets using price action.
Disclaimer: besides the rules, the below presented figures displays guidelines that elliott waves may form. Guidelines are tendencies, not set in stone rules

b- Diagonal Waves ( Wedges )
Another form of motive waves are diagonals, they appear in the beginning of a larger trend, called leading diagonal and at the end of the larger trend, called ending diagonal
They are five-wave structures in the direction of the main trend within which wave 4 almost always moves into the price territory of (overlaps) wave 1, breaking the rule of impulse motive wave
Diagonals take a wedge shape within two converging lines

Elliott was careful to note that these patterns do not provide any kind of certainty about future price movement, but rather, serve in helping to order the probabilities for future market action. They can be used in conjunction with other forms of technical and fundamental analysis , including technical indicators, to identify specific opportunities.

Technical Indicators

Using various technical indicators among elliott wave practitioners is not so common, except few, probably the common one used is a kind of momentum indicator , such as RSI or MACD , to detect divergencies

Fibonacci retracement and extension drawing tools are essential for elliott wave practitioners. In todays computerized era many of the darawing tool’s auto indicator versions are availabe on the trading platforms, such as Auto Fib ( where and how tp apply )

Elliott Wave Oscillator ( EWO ) , is inspired by the Elliott Wave principle and helps counting the waves

Volume and Volume Profile ( Vol / Vol Profile) combined with price action is esential in technical anlaysis and for elliott wave practitioners helps to identify impulse and correction phases

Other indicators that are referred among elliott wave practitioners
Pitchforks ( how to apply ), Pitchfans, FibFans ( how to apply ), FibChannels ( how to apply ), FibTime, LinReg Channel ( what it is ), Raff Regression Channel ( what it is ), etc