Every line of text and every image you add is its own layer, with its own font, color, outline, size, rotation and opacity. Put a sticker or a logo on top of the photo, or send it behind the text with Back. There are thirteen fonts, from Anton (the free stand-in for Impact, which most phones don't have) to handwriting, comic and pixel faces, and they're bundled with the page, so the meme looks the same on every device. Undo covers every change to the text and layers, and each drag counts as one step.
Caption puts the text in a white band above the picture, the way memes often look when they're shared as screenshots. Poster puts the picture in a black frame with a big title and a smaller line underneath. Your pictures never leave your device: the meme is drawn in the browser, and they aren't sent anywhere.