1) The lyrical content of the songs are usually very gore-related, awash with medical terms, and other stomach-churning bodily functions. While grindcore can talk about such subjects, grindcore tends to focus its lyrical content more on political issues.
For example, the goregrind band Last Days of Humanity's songs focus on these gore-related topics, with titles such as "In Advanced Haemorrhaging Conditions", "Covered With Feces as Decoration", and "Cataleptic Liver Explosion".
2) The most obvious difference between goregrind and grindcore is its use of pitch-shifted vocals, which creates an extremely low gurgle noise. This noise can be compared to a deep belch. Due to this, the lyrics are generally rendered incomprehensible.
3) The guitar riffs and overall sound have more of a "metal" feel" than grindcore, which has more of a hardcore punk dominated sound.
However, the two genres are similar in many ways. Both tend to have very short songs, and are very fast, chaotic, and the lyrics are typically difficult, if not impossible, to comprehend.
Major bands include the following:
Cock and Ball Torture
Last Days Of Humanity
Carcass most definitely.