Tensorflow tutorial "MNIST For ML Beginners"

MNIST_for_ML_beginners.py

from __future__ import print_function

from tensorflow.examples.tutorials.mnist import input_data
mnist = input_data.read_data_sets("MNIST_data/", one_hot=True)

import tensorflow as tf

x = tf.placeholder(tf.float32, [None, 784]) 

W = tf.Variable(tf.zeros([784, 10]))
b = tf.Variable(tf.zeros([10]))
y = tf.nn.softmax(tf.matmul(x, W) + b)

y_ = tf.placeholder(tf.float32, [None, 10])
cross_entropy = tf.reduce_mean(-tf.reduce_sum(y_ * tf.log(y), reduction_indices=[1]))

correct_prediction = tf.equal(tf.argmax(y, 1), tf.argmax(y_, 1))
accuracy = tf.reduce_mean(tf.cast(correct_prediction, tf.float32))

train_step = tf.train.GradientDescentOptimizer(0.5).minimize(cross_entropy)

with tf.Session() as sess:
  sess.run(tf.initialize_all_variables())

  max_steps = 1000
  for step in range(max_steps):
    batch_xs, batch_ys = mnist.train.next_batch(100)
    sess.run(train_step, feed_dict={x: batch_xs, y_: batch_ys})
    if (step % 100) == 0:
      print(step, sess.run(accuracy, feed_dict={x: mnist.test.images, y_: mnist.test.labels}))
  print(max_steps, sess.run(accuracy, feed_dict={x: mnist.test.images, y_: mnist.test.labels}))

Hi,
I am new to ML, please tell me what does this code do? i coped this code and executed in my google colab and landed till it showed extracting

Appreciate a response asap.