A time interval, with respect to charting can be defied as a passage of time during which trades take place.
Within a time interval many trades take place, the best way to summaries all the trades during a time interval is by capturing the Open, High, Low and Close (OHLC) data.
If you are talking about 1 minute time interval, you are essentially talking about visualizing the summary of all the trades that happened during that minute. So for every 1 minute you will have 1 set of OHLC. This means within 1hr, you will have 60 data points.
You can change the time interval to whatever frequency you want, for example a 5 min time interval summarizes all the trades that span out within that 5 minute duration.
One word of caution - short time interval like 1,5 and 10 mins have lot of noise in it and less of information. What you should be looking for is information and information is not generated on a minute by minute basis. So begin with maybe 1 hour or even better end of day time frequency.
Time interval is sampling interval at which price is marked for further analysis