My church offers it seventeen times a week, so I suspect we're pretty "high".
The distinction is made within the "big umbrella" of the Episcopal church - not between denominations. The "big umbrella" or wide scope of church practices within the church arose from the attempts of Elizabeth I (and other sovereigns after her) to include as many of the divergent beliefs of English Christians within the scope of the official, national Established Church of England. This concept transferred itself to America with the Episcopal church.
"High" versus "Low" includes two separate issues: liturgical practices and theological beliefs. This was also true in Elizabethan England.
The highest of the high churches (a/k/a "Catholic Lite") from a liturgical point of view include everything you would see in a very traditional Catholic church. Physically, you will see a very traditional sanctuary with a Tabernacle, prominent font, kneelers, elaborate altar furniture (including cloths color keyed to the liturgical year), beautiful vestments on the priests, statues of saints, and precious communion plate. Incense and the ringing of a small bell at the elevation of the Host (during the Mass) are often seen. (Hence the nickname for a High church, "Smells and Bells".) From a theological point of view, the high church acknowledges the Real Presence in the Blessed Sacrament, encourages frequent communication (usually offered daily or even twice daily), offers individual confession, and may have Eucharistic Adoration, Rosary recitation, and other customs generally considered Catholic. (This wing of the church arose largely out of the 19th century Oxford Movement that sought to bring Catholic practices back into the Anglican Church. It migrated to America rather recently!)
The low church in physical appearance resembles your average main line Protestant church -- also in doctrine. The sanctuary is much less elaborate, usually with a plain altar and minimal decoration. Priests (who may call themselves ministers instead) wear plain black vestments as a general rule, although they usually have a chasuble for celebrating communion it is very simple. Communion is given much less frequently - although this is really a change that came in with the revision of the Prayer Book in '79 to come more in line with Catholic practice. Even VERY high Episcopal churches used to offer communion only every fourth Sunday. (This was true at the Cathedral in Atlanta, where I was baptized, confirmed and married). Low churches tend to be very vague on doctrine, but if pressed they will acknowledge that they believe the Sacrament to be only "symbolic". Low churches may be evangelical and Scriptural in their orientation, or NOT. The question of whether an Episcopal Church is evangelical or charismatic is a separate issue from "low" or "high". I have attended low churches that were not particularly evangelical, as well as high churches that were.
That is probably more than you wanted to know. Here's a rhyme to keep them straight:
Low and lazy.
Middle and hazy.
High and crazy.
;-) . . . .speaking of course as a "nosebleed high Anglican," myself.