A Trend in very simple terms refers to a consistent change in prices.

Trends will differ from support/resistance in that trends will represent a change in forex prices while support and resistance will represent a barrier to price changes.

A rising trend refers to successive higher lower prices. In this case the bulls are said to be in control.

A falling trend refers to successive lower higher prices. In this scenario, the bears are in control.

There are a number of popular trend following indicator which include moving averages, trendlines, MACD, and candlesticks.