The speaker is growing close to someone they have only ever met through written messages. They have never seen this person's face, heard their voice, or watched them smile, and yet they feel they know them. The poem keeps circling back to that gap between feeling and proof.
What makes the poem touching is its uncertainty. The speaker builds a picture of the other person in their imagination, but admits they have no idea how accurate it is. Without tone of voice, tears, laughter or gestures, all they have are typed words, and they can only hope those words are sincere. They even wonder whether they are imagining the person altogether.
The mood is tender, hopeful and a little wistful. Repeating the opening lines near the end shows that nothing has changed, but the closeness has grown anyway. The final line, wishing the words would "come to life," sums up the longing: the speaker wants the person behind the screen to become real.