Herbal teas such as lemon ginger tea are more properly called tisanes or infusions, because they don't have any tea leaves in them. Lemon ginger tea is usually made from ground or fresh-shaved ginger and lemon juice or zest. It can be bought in bags or made at home. Make with 1 tsp of powdered ginger per cup of boiling water and add lemon juice to taste. It's good for mild ailments.
Hot or cold ginger tea, with or without lemon, is good for easing nausea brought on from overeating, motion sickness or post-operative nausea. However, the Mayo Clinic notes that more tests need to be done to determine if this is because of the ginger or to the placebo effect.
Tea Bliss notes that ginger lemon tea has been used in China for more than 2,500 years to help increase the appetites of those in emotional distress or fighting an illness.
Ginger tea, with or without lemon, can also help to relieve indigestion and the bloated feeling that comes with gas, because it can help muscles to relax.
Ginger tea has a warming effect on the body, with or without lemon. This is good for quickly warming up people with chills or who have been soaked in a sudden rain.
"A Review of 12 Commonly Used Medicinal Herbs" (Archives of Family Medicine, 1998) notes that the only known side effect of ginger or ginger tea is heartburn.
Lemon juice can not only help make ginger tea more palatable, but it also adds vitamin C and antioxidants.