What is Lactobacillus?
Short answer: lactobacillus is a bacteria
Long answer: Lactobacillus is a "good" bacteria that lives in your digestive tract. It helps breakdown foods and food sugars for improved digestion. It's also found in foods like yogurt (totally normal; all yogurts have it; you can't make yogurt without it).
Lactobacillus ends with the "bacillus" suffix. That means rod shaped. If the suffix was -cocci or -coccus the bacteria would be round. If it was -spirilla or -spirillus the bacteria would be spiral shaped. Lactobacillus are shaped like rods.
They are also facultative anaerobes. That means they can survive in the presence of oxygen and without oxygen. Because they mainly live in the digestive tract, which is an oxygen free zone, the by product of their cellular respiration and ATP production is lactic acid. Thus the name "lacto."
Lactobacillus is a gram-positive bacteria, which means that they take up the crystal violet stain.