adds browser rendering note

doc/getting_started.md

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 # Getting Started with Torque.js
 
-Torque.js is a JavaScript library that enables you to display animated maps using time series data. Torque.js uses a [special tile specification](https://github.com/cartodb/torque-tiles), which consists of JSON representations of multidimensional data with geospatial coordinates.
+Torque.js is a JavaScript library that enables you to display animated maps using time series data. Torque.js uses a [special tile specification](https://github.com/cartodb/torque-tiles), which consists of JSON representations of multidimensional data with geospatial coordinates. The Torque library parses these tiles and renders them in the browser.
 
 **Tip:** Torque is both a spatial and temporal aggregator. It does not plot your exact lat/lon points, it lays an invisible grid over your map, and draws one marker for each grid cell that contains points (representing an aggregation of all of the points in the grid cell). You can control the size of this grid with the CartoCSS [`-torque-resolution`](/cartodb-platform/cartocss/properties-for-torque/#torque-resolution-float) property. You are also able to control the type of aggregation with the CartoCSS [`-torque-aggregation-function`](/cartodb-platform/cartocss/properties-for-torque/#torque-aggregation-function-keyword). For more details, see the wiki page about how [Torque aggregates data](https://github.com/CartoDB/torque/wiki/How-spatial-aggregation-works).