There are three types of search modes in Splunk: Fast Mode, Smart Mode, and Verbose Mode:
If you want your searches to be faster, use Fast Mode. Fast mode will not attempt to generate fields during search time, unlike the default smart mode. This is very good to use when you do not know what you are looking for. Smart Mode looks for transforming commands in your searches. If it finds these, it acts like fast mode; if it doesn't, then it acts like verbose mode. Verbose Mode means that the search will provide as much information as possible even though this may result in significantly slower searches.