API

API = Application Programming Interface.

Betfair and Betdaq platforms utilize a grid" style betting interface. This is perfectably acceptable for the placing of "regular" bets and wagers. The grid interface is more than adequate for 90% of exchange punters.

However, in the fast-changing environment of sports trading something else was needed. Something more reponsive and faster. Thus the first API's were constructed.

There are many bespoke API's available. Most of them apply a charge or rental for their use. I have tried most of them, and I will guarantee this -- by some considerable margin one particular API is better than the rest and it is absolutely FREE. It is the "Geeks Toy"  available for free download HERE

An API is a direct entrance into Betfairs markets -- bypassing the regular Betfair interface. Thus, Backs and Lays can be transacted more quickly.
The response time with an API is faster, and the refresh rate ( displays of up-to-date odds and amounts of money available) can be set at sub-second intervals.
An API allows the end user to customise the application to his own preferences; the trader can set his preferred market display styles, staking level buttons, refresh rate, and myriad other options.

And crucially, the API incorporates a constantly updating Weight-Of-Money indicator along with an alternative interface known as the "Ladder".

Considering the fast response, functionality and multi-tool features of the interface, i is essential that the trader with serious ambition should become familiar with the use of the API.
You really do have to use an API as your default trading interface.