Recording your survey or questionnaire on a tally chart means the data is already collected into groups and you will not need to group it later on.
Investigation example
To investigate the most popular colour of car passing your house over the course of an hour, it is easier to draw tally marks in one of five rows than to write red, blue, silver, silver, red, other, black, etc.
If you use a tally chart, you could note down the colour of the cars as they pass, by quickly making a tally mark, and then find the total frequencies at the end of the one-hour period.