An event-related potential (ERP) is the measured brain response that is the direct result of a specific sense|sensory, cognition|cognitive, or motor system|motor event.
Those brain response can be measured with electroencephalography (EEG) using devices such as Enobio. EEG reflects thousands of simultaneously ongoing brain processes. This means that the brain response to a single stimulus or event of interest is not usually visible in the EEG recording of a single trial. To see the brain's response to a stimulus, the experimenter must conduct many trials (usually in the order of 100 or more) and average the results together, causing random brain activity to be averaged out and the relevant waveform to remain, called the ERP.
These stimuli can be visual, auditory, tactile and even olfactory and gustatory. In order to record those event-related potential the recording set-up needs to synchronise very accurately both the stimuli presentation and the EEG recording device. Commonly the software in charge of presenting the stimuli send a marker to the EEG recording system each time a stimuli is presented. If the triggers are properly recorded along with the EEG signal, an automatic pre-processing step can automatically cut the signal in epochs for further averaging.