Much like the confusing word pair ser and estar, saber and conocer both mean the same thing in this case, "to know." Translating from Spanish to English is no problem, but translating from English to Spanish requires us to know which verb to use and when.
Because there are some irregularities, let's look at the present tense conjugations of both verbs.:
Now let's look at when to use them.
When to Use Conocer
Conocer means "to know people and places," or better yet, "to be acquainted with." For example:
Yo conozco a Michael Phelps.
I know Michael Phelps.
Ella conoce muy bien la ciudad de Denver.
She knows the city of Denver well.
No conocemos este barrio.
We're not familiar with this neighborhood.
When to Use Saber
Saber means "to know facts and information." Consider the following examples:
Yo sé cuantas medallas ganó Michael Phelps.
I know how many medals Michaels Phelps won.
Ella sabe la historia de Denver.
She knows the history of Denver.
No sabemos donde está la casa.
We don't know where the house is.
Note: Saber can also mean "to taste," for example:
La comida sabe muy bien.
The food tastes very good.
Saber + infinitive
When followed by an infinitive saber means "to know how." Notice there is no need to include the word como:
Yo sé nadar.
I know how to swim.
Ella sabe investigar.
She knows how to research.
Saben ir a su casa.
They know how to get to his house.
Saber and Conocer in the Preterite
Note: Conocer can also mean "to meet" in other tenses: Voy a conocer a la nueva estudiante hoy.
Considering what happens to these verbs when they're conjugated in the preterite may also help illustrate the differences. In the preterite conocer becomes "to meet." Saber becomes "to find out":
Yo conocí a la nueva estudiante ayer.
I met the new student yesterday.
Yo supe que es de Argentina.
I found out that she's from Argentina.