The middle of the lower part
The 《象形字典》（Pictography Dictionary) explains the character: the surrounding heart is character 欠，which original means that open mouth, breath out, or speak softly. So the meaning of the character is "To care from one's heart, to show love in a soft voice".
Let's see its small script first
It is all similar to big seal script except there is an extra 夕 alike part on the bottom, which is an up-down 止 (foot). So the small seal script has all the meaning of big seal script, plus "To follow the love anywhere with ones foot".
Its clerical script is
The top part above the 心 is a hand, the original 欠 disappears. Now we have a heart in the middle, a hand on the top, and a foot on the bottom. The meaning of the character becomes "To care with you hands, To love with you heart, To follow the love where ever it goes".
Its current standard printing script for simplified character
The difference between the traditional and simplified characters above is that there is "心“ (heart) in traditional character but not in simplified character.
Many people feel if no Heart, then no Love. So it is a bad simplification.
Its Pinyin is "Ai4".