It is not always possible to know exactly who looked at your tweets on Twitter unless readers have favorited or retweeted tweets, or corresponded with the user. However, Twitter has an analytical service that measures exactly how many people read and engage with your tweets.
The service, called Tweet Activity, can be accessed by opening analytics.twitter.com in a browser tab. If a user is logged into his Twitter account, the number of people who saw his tweets and statistics about his followers since the account was created appear. The tweet statistics are listed as impressions (views) and engagements (retweets and favorites). The service also lists a total of how many views or impressions the Twitter user has had over a 28-day period.